SIIA'ICULTUKr; OF WKSTERiX Yl-XLOW PINE; 881 



But they have not appreciated the slow changes in type due to the 

 gradual succession which takes place in plant formations. It has not 

 been until the last decade that a beginning was made in this country to 

 study forest types on the basis of plant ecology. As is known, in the 

 process of plant succession a plant formation undergoes slow changes 

 in which different species gradually succeed each other and the forma- 

 tion works toward an ultimate society called the climax. This can best 

 be illustrated in the forest by the examples in lodgepole pine and Doug- 

 las fir. In lodgepole pine, Clements - found two more or less distinct 

 types of forest, one a pure even-aged lodgepole pine forest and the 

 other a mixed uneven-aged forest of lodgepole pine, Douglas fir and 

 Engelmann spruce. He found that when the pure even-aged lodgepole 

 pine forest became mature and advanced to overmaturity without suf- 

 fering from any accident, such as holocaustic fire, other species invaded 

 the stand as old lodgepole trees began to fall here and there throughout 

 the stand in the process of loss through old age, fungous and insect 

 attack. These invaders were not lodgepole pine seedlings, but seed- 

 lings of the more tolerant Douglas fir and Engelmann spruce. Lodge- 

 pole pine being intolerant cannot well reproduce under its own over- 

 wood and, in any event, cannot compete with tolerant species in so 

 reproducing. As veterans in the lodgepole pine overwood gradually 

 toppled over, the Douglas fir and Engelmann spruce filled the openings 

 and in this way a truly mixed and uneven-aged forest of these three 

 species occupied the ground where formerly had been a pure even- 

 aged stand of lodgepole pine. But where the pure even-aged lodgepole 

 pine forest upon maturity suffered a devastating fire, Clements found 

 that a pure even-aged stand of lodgepole pine succeeded to make another 

 forest exactly like the one that had been destroyed. Unless the pure 

 lodgepole pine forest is destroyed by fire or is clear cut by man, it will 

 inevitably, through slow stages of succession, develop into the mixed 

 uneven-aged forest described above which the ecologist calls the cHmax 

 forest of lodgepole pine. In the case of Douglas fir, Hofmann ^ found 

 that when the pure even-aged Douglas fir forest is allowed to advance 

 to overmaturity without destructive accident to the stand, a similar 



^ Clements, F. E. "The Life History of Lodgepole Burn Forests." U. S. 

 Forest Service Bulletin 79, 1910. 



^ Hofmann, J. V. "Natural Reproduction from Seed Stored in the Forest 

 Floor." Journ. Agr. Research, V. 11, No. 1, 1917. "The Establishment of a 

 Douglas Imh Forest." Ecology, Vol. L No. 1, 1920. 



